Allow to manually bump carts blocking a voucher

src/pretix/control/templates/pretixcontrol/vouchers/detail.html

@@ -10,14 +10,26 @@
         <div class="alert alert-warning">
             {% trans "This voucher already has been used. It is not recommended to modify it." %}
             <ul>
-            {% for order in voucher.distinct_orders %}
-                <li><a href="{% url "control:event.order" event=request.event.slug organizer=request.event.organizer.slug code=order.code %}">
-                    {% blocktrans with code=order.code %}Order {{ code }}{% endblocktrans %}
-                </a></li>
-            {% endfor %}
+                {% for order in voucher.distinct_orders %}
+                    <li><a href="{% url "control:event.order" event=request.event.slug organizer=request.event.organizer.slug code=order.code %}">
+                        {% blocktrans with code=order.code %}Order {{ code }}{% endblocktrans %}
+                    </a></li>
+                {% endfor %}
             </ul>
         </div>
     {% endif %}
+    {% if redeemed_in_carts %}
+        <div class="alert alert-warning">
+            {% blocktrans trimmed with number=redeemed_in_carts %}
+                This voucher is currently used in {{ number }} cart sessions and there might not be free to use until the cart sessions
+                expire.
+            {% endblocktrans %}
+            <p class="text-right">
+                <a href="{% url "control:event.voucher.deletecarts" organizer=request.event.organizer.slug event=request.event.slug voucher=voucher.id %}" class="btn btn-default"><i class="fa fa-trash"></i> {% trans "Remove cart positions" %}</a>
+            </p>
+            <div class="clear"></div>
+        </div>
+    {% endif %}
     <form action="" method="post" class="form-horizontal">
         {% csrf_token %}
         {% bootstrap_form_errors form %}

src/pretix/control/urls.py

@@ -276,6 +276,8 @@ urlpatterns = [
         re_path(r'^vouchers/(?P<voucher>\d+)/$', vouchers.VoucherUpdate.as_view(), name='event.voucher'),
         re_path(r'^vouchers/(?P<voucher>\d+)/delete$', vouchers.VoucherDelete.as_view(),
                 name='event.voucher.delete'),
+        re_path(r'^vouchers/(?P<voucher>\d+)/deletecarts$', vouchers.VoucherDeleteCarts.as_view(),
+                name='event.voucher.deletecarts'),
         re_path(r'^vouchers/add$', vouchers.VoucherCreate.as_view(), name='event.vouchers.add'),
         re_path(r'^vouchers/go$', vouchers.VoucherGo.as_view(), name='event.vouchers.go'),
         re_path(r'^vouchers/bulk_add$', vouchers.VoucherBulkCreate.as_view(), name='event.vouchers.bulk'),

src/pretix/control/views/vouchers.py

@@ -50,6 +50,7 @@ from django.urls import resolve, reverse
 from django.utils.functional import cached_property
 from django.utils.html import format_html
 from django.utils.safestring import mark_safe
+from django.utils.timezone import now
 from django.utils.translation import gettext_lazy as _
 from django.views.generic import (
     CreateView, DeleteView, ListView, TemplateView, UpdateView, View,
@@ -181,6 +182,38 @@ class VoucherTags(EventPermissionRequiredMixin, TemplateView):
         return VoucherTagFilterForm(data=self.request.GET, event=self.request.event)
 
 
+class VoucherDeleteCarts(EventPermissionRequiredMixin, DeleteView):
+    model = Voucher
+    template_name = 'pretixcontrol/vouchers/delete_carts.html'
+    permission = 'can_change_vouchers'
+    context_object_name = 'voucher'
+
+    def get_object(self, queryset=None) -> Voucher:
+        try:
+            return self.request.event.vouchers.get(
+                id=self.kwargs['voucher']
+            )
+        except Voucher.DoesNotExist:
+            raise Http404(_("The requested voucher does not exist."))
+
+    @transaction.atomic
+    def delete(self, request, *args, **kwargs):
+        self.object = self.get_object()
+        success_url = self.get_success_url()
+
+        self.object.log_action('pretix.voucher.carts.deleted', user=self.request.user)
+        CartPosition.objects.filter(addon_to__voucher=self.object).delete()
+        self.object.cartposition_set.all().delete()
+        messages.success(request, _('The selected cart positions have been removed.'))
+        return HttpResponseRedirect(success_url)
+
+    def get_success_url(self) -> str:
+        return reverse('control:event.vouchers', kwargs={
+            'organizer': self.request.event.organizer.slug,
+            'event': self.request.event.slug,
+        })
+
+
 class VoucherDelete(EventPermissionRequiredMixin, DeleteView):
     model = Voucher
     template_name = 'pretixcontrol/vouchers/delete.html'
@@ -262,6 +295,15 @@ class VoucherUpdate(EventPermissionRequiredMixin, UpdateView):
             'event': self.request.event.slug,
         })
 
+    def get_context_data(self, **kwargs):
+        ctx = super().get_context_data(**kwargs)
+        redeemed_in_carts = CartPosition.objects.filter(
+            voucher=self.object, event=self.request.event,
+            expires__gte=now()
+        ).count()
+        ctx['redeemed_in_carts'] = redeemed_in_carts
+        return ctx
+
 
 class VoucherCreate(EventPermissionRequiredMixin, CreateView):
     model = Voucher